It is known that hydrodynamic bearings can provide not only good centering of a rotating shaft with respect to the bearing, but they also have a self-lubrication capability.
The most important problem to be solved in designing lubrication systems for hydrodynamic bearings is the problem of ensuring a non-stop lubricant supply to the bearings irrespective of any failures in electric power supply systems and structural members of the lubrication system.
An interruption of lubricant supply to the bearings even for a very short time results in failure of the bearings and in a number of applications even in failure of the equipment incorparating such bearings.
This problem is generally solved by redundancy. However, redundancy brings about a substantial increase in size and weight of the system; in addition, such structural arrangements are sophisticated and unreasonable from a practical viewpoint and the cost of such a system is high. Therefore, there is a long felt need to provide a simple, compact and inexpensive lubrication system which is highly reliable.
Known in the art is a device for lubricating hydrodynamic bearings, comprising an oil tank with a pump which is connected to the bearings via a delivery line (cf. U.S. Pat. No. 4194796, Int. Cl. F 16 C 39/04, Sept. 5, 1978).
The device incorporates a special accumulator with two chambers, one chamber being filled with a gas under pressure supplied from an auxiliary vessel and the other chamber being filled with oil. In case of failure of the pumps there is a danger that metal surfaces of the bearings can contact each other because of an oil pressure drop. The accumulator rules out this failure. This system is, however, complicated in structure because, apart from the conventional use of two pumps as redundancy, it also requires auxiliary pipelines, a number of valves and a compressed gas source.
As a result, size and cost of the device are substantially higher.
Also known in the art is a device for lubricating hydrodynamic bearings in which an attempt was made to reduce auxiliary and redundant equipment (cf. U.S. Pat. No. 3563344, Int. Cl. F 16 N 7/40, Nov. 19, 1968). This device, which comprises an oil tank with pumps connected to the bearings via a delivery line, incorporates a distribution means which is adapted to supply oil to the bearing during normal operation of the pump and upon its failure. This device also calls for a number of auxiliary elements such as a redundant pump, an auxiliary tank and an auxiliary valve. Moreover, this device can only be used for lubrication of hydrodynamic bearings of special design having an auxiliary passage. This makes the device very complex and results in increased cost thereof.